CLASPs and LL5s cooperate in maintaining BM integrity in lateral epiblast cells. (A and C) Electroporated at low concentrations, eGFP-LL5α (A) and eGFP-LL5β(C) have a basal cortical localization (white arrows). (B and D) Overexpression of eGFP-LL5α (B) and eGFP-LL5β (D) in streak cells causes ectopic laminin expression (yellow arrows). ps, primitive streak. (E) Quantification of laminin breakdown when LL5s or LL5s + CLASP1 are knocked down with MOs in lateral epiblast cells. LL5 and CLASP1 knockdown leads to strong laminin breakdown phenotypes. (F–I) Examples of phenotypes caused by LL5α and β double MO (F), LL5α (G), or LL5β (H) single MO, standard control MO (I), and LL5 and CLASP1 triple MO (J) knockdown. White arrows in F–H and J indicate premature BM breakdown. Yellow arrows in I indicate normal BM in standard MO-receiving cells. Arrowheads indicate the streak midline. Bars, 20 µm.